Poland has to conduct further reforms of the tax system, which shows a lot of imperfection and necessitates a preventing of the high budget deficit. It seems a proper solution to keep the current structure of the tax system and to focus on issues concerning detailed solutions within the specific taxes. A fiscal functions of taxes should be considered a significant priority. The economic success of the countries which introduced linear income taxes (Baltic countries and Russia) serves as an encouragement to copy the solutions adapted there. A lot of doubts, however, arise in connection with a too strong diversity of individuals' incomes, moving the burden of taxation on medium income groups and the rates of linear taxes. As a result, it seems difficult to decide whether the linear income tax on natural persons' incomes should be introduced in Poland. The consequences of a decision like this one are hard to predict.